Display apparatus including character enhancement

ABSTRACT

A readout means provides encoded information representing each character to be written on a cathode-ray tube screen as well as five enhancement levels. The output of the readout means is decoded into a video format and fed through a selectively actuated inverter for control of the cathode-ray beam. In response to signals at one of two of the memory enhancement output levels, the intensity of the displayed character is uniformly reduced or caused to pulsate. In response to an underline signal at one of the enhancement levels coinciding with a selected scan line, the inverter is actuated writing a row of dots under a desired character. A cursor signal at one of the enhancement levels actuates the inverter producing a cursor indication upon the screen and a tabulate enhancement signal creates a tabulate mark upon the screen.

Unite States Patent Man, Jr. et al.

[ DISPLAY APPARATUS INCLUDING Primary Examiner-David L. Trafton CHARACTER ENHANCEMENT Attorney, Agent, or Firm-W. K. Serp; J. L. Landis [75] Inventors: Theodore .1. Mau, Jr.; John L.

Peterson, both of Ch1cago, Ill. [57] ABSTRACT [73] Asslgnee: Teletype Corporation Skokle A readout means provides encoded information repre- [22] Filed: Aug. 14, 11973 senting each character to be written on a cathode-ray tube screen as well as five enhancement levels. The [21] Appl' 388286 output of the readout means is decoded into a video format and fed through a selectively actuated inverter u 4 /1725 for control of the cathode-ray beam. In response to [51] Int. Cl. G08b /36 signals at one of two of the memory enhancement out- [58] Field of Search 340/324 AD, 172.5, 324 A put levels, the intensity of the displayed character is uniformly reduced or caused to pulsate. In response to [56] References Cited an underline signal at one of the enhancement levels UNITED STATES PATENTS coinciding with a selected scan line, the inverter is ac- 3 336 587 8/1967 Brown 340/324 A tuated writing a row of dots under a desired character. 3:346:853 /1967 340N725 A cursor signal at one of the enhancement levels actu- 3,531,796 9/1970 Kiesling 340/324 A ates the inverter Producing a Cursor indication p 3,581,290 5/1971 Sugarman 340/1725 the screen and a tabulate enhancement signal creates 3,609,743 9/1971 Lasoff et a1. 340/324 AD a tabulate mark upon the screen. 3,648,272 3/1972 Schroder et al. 340/324 A 14 Claims, 2 Drawing Figures I 1 I 1 I I I l 5 I I l l I I I l 1 I I I l l I If I l I I l I l I I I oooooo. ooooooooooo 2- ooooooo ooooooo 0000000 0 oo o 3- o o o o oooooooo ooooooo o o-28 o o ooooooo ooooooo 5-- o/ o o o oooooooo ooooooo oooo oooo oooo o ooooo oooo 7- o o o ooooooo ooooooo o o o o ooooooo ooooooo o o o o oooooooo ooooooo I oooooo oooo-ooo ooooooo o oo o l noooooooooooooooooo I o oo oooooo o ooooo 13- g asdoooooooooooooooo |4 96 ooooooooooooooo o TOTAL 0F 80 CHARACTERS PER ROWUZO DOTS) \HORIZONTAL RETRACE TIME =20 CHARACTERS I W f HORIZONTAL VERTICAL RETRACE 1 i 4' RETRACE LIL' L L'EL 38 \\l I I| DOT C FSQ SCAN CHARACTER 1 VERTICAL. GENERATOR COUNTER COUNTER COUNTER COUNTER RETRACE DISPLAY APPARATUS INCLUDING CHARACTER ENHANCEMENT Reference is made to copending US. Pat. application Ser. No. 388,296, filed Aug. I4, 1973, by Harold D. Cook, entitled Display Apparatus with Visual Segment lndicia and having a common assignee herewith.

BACKGROUND OF THE INVENTION This invention generally relates to an apparatus for providing a visual display of digitally encoded information, and more particularly relates to such an apparatus which includes means for enhancing the presentation and uniqueness of selected characters being displayed.

Various systems have been suggested for providing a visual display of stored coded information. Generally, the encoded information is fed into a storage memory or readout means from which each coded character is selectively read out, decoded and used to control the beam of a cathode-ray tube. A visual presentation is provided on the tube screen corresponding to the character read out from the memory. The characters may be generated by various methods. One particular arrangement displays each character in the form of a dot matrix written by a plurality of vertically spaced horizontal scans of the electron beam. The beam is pulsed during each scan to produce the desired dot pattern.

To increase the intelligibility of the displayed text, it is frequently desirable to provide certain characters with those unique characteristics available in written or printed format. For example, the operator may find it useful to underline particular characters or words for emphasis or to italicize selected words or phrases. Previously, such editorial freedom has not generally been available in connection with the use of an electronic visual display apparatus.

Occasionally, the operator, utilizes the apparatus to fill in a prearranged form. In this situation, the form is initially displayed upon the screen from a storage memory and the operator fills in the appropriate blank areas with selected information. Further, the form material maybe entered upon the screen with protected characters. That is, the operator is prevented from either intentionally or accidentally altering the form as displayed. For the convenience of the operator, it is desirable if the form format is readily distinguishable from the entered material.

Frequently, one of the operating features of a display apparatus is a tabulation provision which facilitates the use of the apparatus for the tabulation of columns of information in much the same manner as one would use a conventional typewriter. As an aid in entering such tabulations, it is convenient for the operator to be provided with an indication designating the location of each tabulation.

SUMMARY OF THE INVENTION The illustrated embodiment of the invention includes a readout means providing a plurality of coded signal outputs. At least one of the outputs supplies a multithe character signal from the readout means. The readout means additionally provides a first enhancement signal which corresponds to an enhancement characteristic of the character being displayed. Control means are included for selectively applying the enhancement signal to the inverter for inverting the character signal in response to the presence of the: enhancement signal.

The readout means also provides a second enhancement signal which, upon the occurrence of a selected scan line signal, activates the control means for selectively controlling the combination of the second enhancement signal with the character signal. Additionally, a third enhancement signal is provided by the readout means for controlling the overall intensity of the cathode-ray beam during the writing of the displayed character.

It is a main object of this invention to provide a display apparatus including means for enhancing the presentation and uniqueness of various characters displayed. Other objects and advantages of the invention will be more readily appreciated after reference to the following description and accompanying drawings wherein:

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a fragmentary view of the screen of a cathode-ray tube display and a partial diagram of a display apparatus; and

FIG. 2 is a partial diagram which when combined with a diagram of FIG. 1 illustrates a display apparatus including certain features of this invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT GENERAL The characters to be displayed are stored in digital form in a readout means or memory It). The output of the memory 10, upon selected command, provides multilevel signal information representing each character in the form of a parallel seven level ASCII code via lines 13, as well as five extension levels at output ports 14, 16, 18, 20, and 22. In response to a signal level at one of the ports 14 through 22 inclusive, the intensity and/or pattern of the beam of the cathode-ray tube 26 is varied to provide one of the selected character enhancement features illustrated in FIG. I.

As illustrated, each of the individual characters are created by selectively unblanking the cathode-ray beam to illuminate selected dots. 28 in a matrix which is approximately nine dots in width and fourteen dots in height. In practice, the dots are enlarged slightly causing them to merge thereby forming a continuous character as illustrated in FIG. I of McClelland, US. Pat. No. 3,609,749 herein incorporated by reference. The character itself is seven dots in width providing a two dot spacing between individual characters and is nine dots in height providing a five dot spacing between character rows. In response to a highlight signal at the output port 20 of the memory II), the illuminated dots 28 forming a character are caused to flash providing a visual indication to the operator. In response to a protected signal at port 22, the overall intensity of the character is uniformly adjusted so as to make it readily distinguishable from the remainder of the text. In the presence of a tabulate signal from output port 14, a dot 32 is placed at column two, row twelve which indicates the start of a tabulate column. The underline signal at output 18 produces a row of dots 30 extending from columns one through nine at row twelve of the matrix, thus underlining a selected character. Additionally, the display device generates a cursor indication which, in the illustrated embodiment, is a complete matrix rectangle formed by dots in each of the matrix positions with the character and enhancement features formed by blanked dot positions as at 34. The combined presence of various of the enhancement signals provides unique character presentations as will subsequently be related.

TIMING Throughout the following discussion, certain timing relationships are described. It should be understood that these timing relationships are provided to give the reader a better understanding of the operation of the embodiment herein described and not in limitation of the invention. In FIG. 1, the letter E is illustrated as at 35 and is formed by a matrix of the dots 28, seven columns wide and' nine lines high. As previously mentioned the area of the screen assigned to each character is nine dots wide and fourteen dots in height. Serving to determine the spacing of the dots and establish a time base for the apparatus, is a dot generator 36 which in turn drives a character width counter 38 of modulus nine equivalent to the dot width of the raster assigned to a character. Upon the completion of one horizontal scan of each character, the character width counter 38 provides an output pulse the frequency rate of which is equivalent to the time necessary to write the width of one character plus two interspacing dots. Providing an output pulse at the start of each horizontal scan, is a scan character counter 40 having a modulus of one hundred. An entire character line is scanned by the beam and retracted during a time duration equivalent to the generation of one hundred characters. The width of the screen of the cathode-ray tube accommodates eighty characters with ahorizontal retract time equivalent to twenty characters. Serving to trigger the horizontal retrace; a decoded count output from the scan character counter via line 41 is fed to a horizontal retract'unit 42. The output of the scan character counter 40 drives a scan line counter 44 having a modulus of fourteen.

As previously mentioned, the matrix area assigned to each character is approximately nine dots in width and fourteen dots in height. Thus, each fourteen scans of the beam correspond to the writing of an entire horizontal row of characters. The scan line counter 44 generates one output pulse for each fourteen scan lines equivalent to the writing of one character row. Each of the counter levels in the scan line counter are brought out via conductors 46 for decoding purposes to be described. Additionally, the twelfth count output of the modulus fourteen scan line counter 44 is available at line 48 which corresponds to the twelfth scan line which is two scan lines below the base of a written character. The output of the scan line counter 44 is fed to a test row counter 50 modulus twenty-five. The output of the text row counter 50 drives a vertical retrace unit 52. The vertical display area of the cathode-ray tube 26 is of sufficient height to accommodate twenty-four rows of characters with the vertical beam retrace requiring a time equivalent to the writing of one character row.

CHARACTER GENERATION With respect to FIG. 2, the coded character information stored in the memory 10 is selectively read out by means of address lines which are controlled by a memory address (not shown) which does not form a part of this invention. A particular address arrangement suitable for use with the illustrated embodiment is described in US. Patent Application of Harold D. Cook entitled Display Apparatus with Visual Segment Indicia," Ser. No. 388,296, filed on Aug. l4, I973, and having a common assignee with this application, herein incorporated by reference. As illustrated, the output of the memory provides twelve output ports or levels. As previously mentioned, the five output ports relate to the enhancement features, namely tabulation l4, underline 16, cursor 18, highlight 20, and protect 22 and the first seven levels 13 correspond to the seven levels of the ASCII code. The seven levels 13 are fed to the font decoder 23 which serves to convert the ASCII code into a video format suitable for driving the grid of the cathode-ray tube 26. The font decoder 23, includes address ports 56 as well as output ports 58. The address ports 56 of the font decoder 23 are connected to the four parallel address lines 46 provided by the scan line counter 44. The memory 10 presents a selected multilevel encoded character signal to the input of the font decoder 23 and the address lines 46 present a binary level related to the scan line which is the desired decoding scan level for that character. For example, when an encoded letter E is presented to the font decoder 23 from the memory and when the address lines 46 designate scan line six, the output will be unblanked to provide dots at character columns two through five inclusive.

The multilevel output from the font decoder 23 is connected to the input levels 60 of a signal inverter 62 which, in response to a command signal at an invert input 64, reverses the signal polarity on the nine incoming levels 60. Serving to convert the paralleloutput from the inverter 62 into a serial signal for control of the beam intensity of the cathode-ray display tube 26, is a parallel to serial shift register 66. The output from the register 66 is stepped at the frequency rate of the dot generator 36 signal which is coupled via line 68. The shift register 66 is selectively loaded for each character with the output of the inverter 62 in response to a signal from the output of the character width counter 38 via line 70. Thus, the character to be displayed is read out of the memory 10 and the seven parallel ASCII levels 13 are fed to the font decoder 23 whereat they are decoded on a scan line basis. The parallel level output signals from the font decoder 23 are fed to the input 60 of the inverter 62. In the absence of a signal at the invert port 64 of the inverter, the output of the font decoder 23 is passed therethrough to the parallel to serial shift register 66. In response to the output of the register 66, the electron beam of the cathode-ray tube 26 is unblanked during scanning to write one of the fourteen scan lines comprising a character. This process is repeated for each character in a character row and after fourteen scan line levels have been decoded and written, the memory is stepped to the next adjacent character row. 1

CHARACTER ENHANCEMENT The following discussion pertains to those features previously mentioned which serve to enhance the presentation of a selected character and provide the operator with a degree of editorial freedom; that is, the tabulate, underline, cursor, highlight, and protect features. The output from port 22 which is the protect level from the memory 10, is connected to one input of an intensity OR-gate 71, the output of which is coupled through a cathode intensity control circuit 72 to the cathode of the tube 26 for overall control of the cathode-ray beam intensity. Thus, in the presence of a protect level signal, which is associated with the output of a selected encoded character from the memory, the OR-gate 71 will provide a signal to the intensity control circuit 72 which in turn produces a reduction in the overall intensity of the electron beam during the writing of the selected character. As previously mentioned, the presence of the protect signal, indicates that the associated character isnot to be overwritten. In the illustrated embodiment, the light level of the protected character on the screen is less than would be the case for normal display of the remaining material. This feature affords the operator a means for readily identifying those portions of the display which are protected and form part of the displayed form format.

In response to a signal at the high light port 20 of the memory, which is associated with a character read out having an editorial significance, the highlight signal is fed to one input of a highlight AND-gate 74. The alternate input of the AND-gate 74 is connected to the output of a one second timer 76. Thus, in response to a highlight level signal, the output of the one second timer 76 passes to the output of the AND-gate 74 and is fed to one input of the intensity OR-gate 71. The timer signal at the output of the intensity OR-gate 71 serves to modulate the level of the formed character at a visually noticeable pulsating rate. In this way, the character written displays a pulsating intensity providing the operator with a unique indication that this character contains editorial significance.

As previously mentioned, a cursor format in the form of a full dot matrix may be selectively generated. It will be appreciated that when a cursor is located in the same matrix area assigned to a character, the character would normally be obliterated because the dot pattern would include all of the dots forming the character. To prevent a wash-out of the character when the cursor location and character location coincide, the described embodiment illustratesthe character in a reverse outline, or negative image illustrated for the two characters at the right in FIG. 1. The cursor signal from the memory is fed from port 18 to one input of an exclusive OR-gate 78 and the output of the exclusive OR-gate 78 is applied to the invert input 64 of the inverter 62. When an alphanumeric character has been erased from memory, the memory position reverts to a space character at output 13 of the memory. The cursor signal passing through the exclusive OR-gate 78, will invert the space character producing a complete dot matrix upon the screen. Thus, in the absence of a character, the visual cursor indicator is an entirely illuminated rectangle. Assuming, for purposes of illustration, that a character code is present at the input 60 of the inverter 62, the presence of a cursor signal at the invert input 64 will produce an inversion so that the dot matrix corresponding to the selected letter, which would normally be illuminated, in blanked-out and the surrounding area enlightened thus providing an inverted character as at 34 of FIG. 1.

A signal level at the underline port 16 of the memory 10 is coupled to one input of an underline AND-gate 82, the alternate input of the AND-gate 82 being connected to the count twelve output of the scan line counter 44 via line 48. In response to the coincidence of an underline level signal together with the twelfth line output of the counter 44, a coincidence signal is fed to one input of the exclusive OR-gate 78. The coincidence signal passes to the inverter input 64 causing the inverter 68 to invert the input signal thereby producing a row of dots at the twelfth line of the dot matrix as at 30 of FIG. 1. Thus, the coincidence of the twelfth count output of the counter and an underline signal produces a row of dots located two scan lines below the base of the associated character and nine columns wide, as illustrated for the second character from the left in FIG. 1. The coincidence of both the cursor and underline signals at the input to the exclusive OR-gate 78 turns off the input to the invert input 64 of the signal inverter 68 during the writing of the twelfth scan line. This condition generates a cursor with the twelfth scan line blanked as at 80 of FIG. 1 thus preventing wash out of the underline feature in the presence of a displayed cursor.

With respect to the tabulate feature, the tabulateport 14 of the memory supplies, a signal to one input of a tabulate AND-gate 84. Asecond input of the AND- gate 84 is connected to the output of an underline inverter 87 the input of which is connected to the underline port 16 from the memory 10. In the absence of an underline signal, this input will remain high. The third input of the AND-gate 84 is connected to the count twelve output of the scan line counter 44 via line 48. Upon the occurrence of thecount twelve and the tabulate signals, an output signal is applied to a second column input 88 of the dot inverter 60 which corresponds to the second column of the dot matrix. Thus, upon the occurrence of the count twelve output from the scan line character counter 44, and the tabulate signal, a dot will be written in the second row of the twelfth line of the matrix so as to create a tabulation mark as at 32 of FIG. 1.

A particular feature of the illustrated embodiment will be more readily appreciated if it is assumed that both the tabulate and underline signals are present at the output of the memory 10. As previously discussed the coincidence of the tabulate signal, and count twelve of the scan line counter, will produce a dot at column two, line twelve of the dot matrix to which the tabulate signal relates. During the writing of the twelfth scan line the underline signal is applied to the invert input 64 of the inverter 62 through the OR-gate 78. However, as will be described, the presence of a tabulate signal, together with an underline signal, does not result in the wash-out of the tabulate indication. A third AND-gate 89 is indicated having a first input connected to the tabulate port 14 of the memory and a second input connected to the underline port 16. A third input of the AND-gate 89 is fed by the scan twelfth signal via line 48 and upon coincidence of the three input signals to the AND-gate 89 an output signal is coupled via a pair of steering diodes 90 and 91 to inverter inputs 92 and 94 respectively. Inverter inputs 92 and 94 corre spond to the first and third matrix columns as illustrated in FIG. 1. To summarize, in response to the tabulate signal, a signal is applied to input 88 of the inverter 62 generating a dot as at 32. In the presence of both the underline and tabulate signals the underline signal passes through the inverter 87 opening the AND-gate 84 removing the signal from input 88 of the inverter 62, and passes a signal through AND-gate 89 and diodes 90 and 91 to inverter inputs 92 and 94. The combined tabulate and underline signals generate the character pattern illustrated in FIG. 1 at 96 which is a dot pattern at scan line twelve with dot column one and three blanked.

OPERATION operation, the seven parallel levels representing an ASCII character are fed via line 13 through the font de-.

coder 23 and the inverter 62 and serially applied to a control element of the cathode-ray tube 26 by the shfit register 66. The beam intensity is selectively unblanked while scanning across the tube screen creating a character representative dot matrix for each character in the row. The memory also includes five enhancement level outputs which supply the particular enhancement signals for the displayed character. In this respect, the protect 22 and highlight outputs control the intensity of the electron beam. The protect feature reduces the beam intensity during the writing of a protected character while the highlight signal in combination with a timer 76 produces a pulsating character intensity causing the character to stand-out from the remaining text material displayed on the screen. The cursor signal at port l8 and underline 16 features serve to control the invert input 62 of the inverter 60 through which the various decoded characters from the font decoder 23 pass to the parallel to serial shift register 66. In the presence of a cursor signal at port 18, the signal levels applied to the input port 60 of the inverter 62 are inverted thus creating their complement at the input to the parallel toserial shift register 66. With respect to the underline signal 16, a signal is applied to the inverter input 64 of the inverter 62 in response to the scanning of the twelfth line of a character row, thereby producing-an underline below the selected character.

, A tabulation dotis generated in response to a tabulate signal 14 from thememory 10 and is fed to an input 88 of the, inverter62. in response to the scan of the twelfth scan line generating the tabulation dot illustrated at 32.

The simultaneous presence of an underline signal and a tabulate signal produces signals at inputs 92 and 94 of the signal inverter creating a unique character underline. with a tabulate dot set apart by blanked dots at columns one and three of scan line twelve as illustrated at 96. The simultaneous presence of the underline, tabulate and cursor signals produces a cursor matrix with the twelfth scan line displaying a single dot at column two as illustrated at 98. The presence of the cursor and highlight signals at the input of the OR-gate 78 removes the input to the invert port 64 of the inverter 62 during scan line twelve. This allows the tabulate dot to pass through the inverter 62 producing a single dot on scan line twelve at column two.

A display apparatus has been described which provides the operator with a latitude of editorial freedom by providing tabulate, underline, highlight, protect, and cursor indications, both singly and in combination. Although the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood that various changes in character; said readout means providing an underline enhancement signal corresponding to an enhancementcharacteristic of the character being displayed;

a selectively actuated inverter receiving said character signal from said readout means for controlling the intensity of the cathode-ray tube electron beam;

a scan line counter providing an output signal related to the writing of a selected scan line on the display screen; first control means actuated by said scan line signal in the presence of said underline enhancement signal for generating a first control signal; and

said readout means providing a cursor enhancement signal indicating a cursor location, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter thereby displaying an inverted, underlined character on the display screen.

2. The apparatus of claim 1 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.

3. An apparatus for enhancing the presentation of selected characters displayed upon the screen of a cathode-ray tube comprising:

readout means providing a plurality of coded signal outputs, at least one of said outputs providing a multilevel character signal determining the character to be displayed upon the cathode-ray tube screen;

means for selectively controlling the cathode-ray tube beam in accordance with said character signal so as to generate a dot matrix forming the encoded character;

said readout means providing an underline enhancement signal corresponding to an enhancement characteristic of the character being displayed;

a selectively actuated inverter receiving said character signal from said readout means for controlling the intensity of the cathode-ray tube electron beam;

a scan line counter providing an output signal related to a selected scan line being written on the display screen;

first control means actuated by said scan line signal in the presence of said underline enhancement signal for generating a first control signal serving to selectively actuate said inverter during said scan line; and

. 7 so asto generate a dot matrix forming the encoded W said readout means providing a tabulate enhancement signal indicating a tabulate location, said first control means further including means activated by said scan line signal and said tabulate enhancement signal for selectively controlling the combination of said tabulate enhancement signal with at least one of said multilevel outputs so as to display a tabulate underline indication on the screen at a selected scan line.

4. The apparatus of claim 3 wherein said readout means provides a cursor enhancement signal, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter thereby displaying an inverted, tabulated, underlined character upon the screen.

5. The apparatus of claim 4 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.

6. The apparatus of claim 4 wherein said readout means provides an intensity enhancement signal (20,22), second control means actuated by said intensity enhancement signal for controlling the overall intensity of the cathode-ray beam during the writing of a displayed character thereby determining the overall illumination intensity of the character so generated.

7. The apparatus of claim 6 wherein said second control means includes means responsive to said intensity enhancement signal for cyclically varying the intensity of the displayed character.

8. The apparatus of claim 3 wherein said control means further includes means for inhibiting the combination of said tabulate enhancement signal with at least one of said multilevel outputs in the presence of said underline enhancement signal.

9. The apparatus of claim 8 wherein said control means includes second means actuated by the simultaneous occurrence of said scan line signal and said underline and tabulate enhancement signals for selectively controlling the combination of said tabulate enhancement signal with at least one of said multilevel outputs.

10. The apparatus of claim 9 wherein said readout means provides a cursor enhancement signal, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter.

11. The apparatus of claim 10 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.

12. An apparatus for enhancing the presentation of selected characters displayed upon the screen of a cathode-ray tube comprising:

readout means providing a plurality of coded signal outputs, at least one of said outputs providing a multilevel character signal determining the character to be displayed upon the cathode-ray tube 7 screen;

means for selectively controlling the intensity of the cathode-ray tube beam in accordance with said character signal so as to generate a dot matrix forming the encoded character;

said readout means providing a first enhancement signal (14,16) corresponding to an enhancement characteristic of the character being displayed;

a font decoder receiving said character signal from said readout means and converting same to a multilevel output for control of said cathode-ray tube beam intensity;

control means for selectively combining said first enhancement signal with at least one of said multilevel outputs from said font decoder;

a scan line counter providing an output signal related to the scan line being written, said control means being activated by said scan line signal for selectively controlling the combination of said first enhancement signal with at least one of said multilevel outputs from said font decoder; and

a selectively actuated inverter receiving the multilevel output from said font decoder for controlling the intensity of the cathode-ray tube electron beam and means for selectively applying a second enhancement signal (16,18) to said inverter for inverting the input thereof in response to the presence of said second enhancement signal (16,18).

13. The apparatus of claim 12 wherein said readout means provides an intensity enhancement signal (20,22), and control means actuated by said intensity enhancement signal for controlling the overall intensity of the cathode-ray beam during the writing of a displayed character thereby determining the overall illumination intensity of the character so generated.

14. The apparatus of claim 13 wherein said intensity enhancement signal is in the form of a highlight enhancement signal and said control means includes means responsive to said highlight enhancement signal for cyclically varying the overall intensity of the displayed character. 

1. An apparatus for enhancing the presentation of selected characters displayed upon the screen of a cathode-ray tube comprising: readout means providing a plurality of coded signal outputs, at least one of said outputs providing a multilevel character signal determining the character to be displayed upon the cathode-ray tube screen; means for selectively controlling the cathode-ray tube beam in accordance with said character signal so as to generate a dot matrix forming the encoded character; said readout means providing an underline enhancement signal corresponding to an enhancement characteristic of the character being displayed; a selectively actuated inverter receiving said character signal from said readout means for controlling the intensity of the cathode-ray tube electron beam; a scan line counter providing an output signal related to the writing of a selected scan line on the display screen; first control means actuated by said scan line signal in the presence of said underline enhancement signal for generating a first control signal; and said readout means providing a cursor enhancement signal indicating a cursor location, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter thereby displaying an inverted, underlined character on the display screen.
 2. The apparatus of claim 1 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.
 3. An apparatus for enhancing the presentation of selected characters displayed upon the screen of a cathode-ray tube comprising: readout means providing a plurality of coded signal outputs, at least one of said outputs providing a multilevel character signal determining the character to be displayed upon the cathode-ray tube screen; means for selectively controlling the cathode-ray tube beam in accordance with said character signal so as to generate a dot matrix forming the encoded character; said readout means providing an underline enhancement signal corresponding to an enhancement characteristic of the character being displayed; a selectively actuated inverter receiving said character signal from said readout means for controlling the intensity of the cathode-ray tube electron beam; a scan line counter providing an output signal related to a selected scan line being written on the display screen; first control means actuated by said scan line signal in the presence of said underline enhancement signal for generating a first control signal serving to selectively actuate said inverter during said scan line; and said readout means providing a tabulate enhancement signal indicating a tabulate location, said first control means further including means activated by said scan line signal and said tabulate enhancement signal for selectively controlling the combination of said tabulate enhancement signal with at least one of said multilevel outputs so as to display a tabulate underline indication on the screen at a selected scan line.
 4. The apparatus of claim 3 wherein said readout means provides a cursor enhancement signal, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter thereby displaying an inverted, tabulated, underlined character upon the screen.
 5. The apparatus of claim 4 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.
 6. The apparatus of claim 4 wherein said readout means provides an intensity enhancement signal (20,22), second control means actuated by said intensity enhancement signal for controlling the overall intensity of the cathode-ray beam during the writing of a displayed character thereby determining the overall illumination intensity of the character so generated.
 7. The apparatus of claim 6 wherein said second control means includes means responsive to said intensity enhancement signal for cyclically varying the intensity of the displayed character.
 8. The apparatus of claim 3 wherein said control means further includes means for inhibiting the combination of said tabulate enhancement signal with at least one of said multilevel outputs in the presence of said underline enhancement signal.
 9. The apparatus of claim 8 wherein said control means includes second means actuated by the simultaneous occurrence of said scan line signal and said underline and tabulate enhancement signals for selectively controlling the combination of said tabulate enhancement signal with at least one of said multilevel outputs.
 10. The apparatus of claim 9 wherein said readout means provides a cursor enhancement signal, gating means serving to couple said first control signal and said cursor enhancement signal to said selectively actuated inverter.
 11. The apparatus of claim 10 wherein said gating means serves to couple said first control signal to said selectively actuated inverter in the absence of said cursor enhancement signal and serves to couple said cursor enhancement signal to said selectively actuated inverter in the absence of said first control signal.
 12. An apparatus for enhancing the presentation of selected characters displayed upon the screen of a cathode-ray tube comprising: readout means providing a plurality of coded signal outputs, at least one of said outputs providing a multilevel character signal determining the character to be displayed upon the cathode-ray tube screen; means for selectively controlling the intensity of the cathode-ray tube beam in accordance with said character signal so as to generate a dot matrix forming the encoded character; said readout means providing a first enhancement signal (14,16) corresponding to an enhancement characteristic of the character being displayed; a font decoder receiving said character signal from said readout means and converting same to a multilevel output fOr control of said cathode-ray tube beam intensity; control means for selectively combining said first enhancement signal with at least one of said multilevel outputs from said font decoder; a scan line counter providing an output signal related to the scan line being written, said control means being activated by said scan line signal for selectively controlling the combination of said first enhancement signal with at least one of said multilevel outputs from said font decoder; and a selectively actuated inverter receiving the multilevel output from said font decoder for controlling the intensity of the cathode-ray tube electron beam and means for selectively applying a second enhancement signal (16,18) to said inverter for inverting the input thereof in response to the presence of said second enhancement signal (16,18).
 13. The apparatus of claim 12 wherein said readout means provides an intensity enhancement signal (20,22), and control means actuated by said intensity enhancement signal for controlling the overall intensity of the cathode-ray beam during the writing of a displayed character thereby determining the overall illumination intensity of the character so generated.
 14. The apparatus of claim 13 wherein said intensity enhancement signal is in the form of a highlight enhancement signal and said control means includes means responsive to said highlight enhancement signal for cyclically varying the overall intensity of the displayed character. 